The present invention relates to growing and testing any cell type in a multitest format which utilizes a gel forming matrix for the rapid screening of clinical and environmental cultures. The present invention is suited for the characterization of commonly encountered microorganisms (e.g., E. coli, S. aureus, etc.), as well as commercially and industrially important organisms from various and diverse environments (e.g., the present invention is particularly suited for the growth and characterization of the actinomycetes and fungi). The present invention is also particularly suited for analysis of phenotypic differences between strains of organisms, including cultures that have been designated as the same genus and species. In addition, the present invention provides methods and compositions for the phenotypic analysis and comparison of eukaryotic (e.g., fungal and mammalian), as well as prokaryotic (e.g., eubacterial and archaebacterial) cells.
Ever since the golden age of microbiology in the era of Koch and Pasteur, methods for identification of microorganisms have been investigated. Koch""s experimental proof that microorganisms cause disease in the early 1800""s, provided the impetus to study methods to grow and characterize harmful, as well as beneficial microorganisms. Koch""s early experiments to determine the etiology of infectious diseases, led to methods for cultivation of microorganisms on the surface of solid media (e.g., potato slices, see Koch, xe2x80x9cMethods for the Study of Pathogenic Organisms,xe2x80x9d in T. D. Brock, Milestones in Microbiology, American Society for Microbiology, 1961, pp. 101-108; originally published as: xe2x80x9cZur Untersuchug von pathogenen Organismen,xe2x80x9d Mittheilungen aus dem Kaiserlichen Gesundheitsamte 1:1-48 [1881]). These studies eventually led to the development of agar as a culture medium component useful for producing solid media for growing isolated colonies of bacteria. To this day, isolated colonies are required (i.e., xe2x80x9cpure culturesxe2x80x9d) to biochemically identify organisms.
The field of diagnostic and clinical microbiology has continued to evolve, and yet, there remains a general need for systems that provide rapid and reliable biochemical identifications of microorganisms. In particular, it has been very difficult to develop an identification system which is capable of identifying various diverse types of organisms, ranging from the common isolate Escherichia coli to the less commonly encountered actinomycetes and fungi.
Methods and identification systems to characterize microorganisms widely used in industry for production of food and drink (e.g., beer, wine, cheese, yogurt, etc.), the is production of antibiotics (e.g., penicillin, streptomycin, etc.), bioremediation of oil spills, biological control of insect pests (e.g., Bacillus thuringiensis), and the production of recombinant proteins, are still needed. In addition, very few identification methods and systems have been developed for environmental use and there remains a need for simple and generally useful identification methods of many organisms. In particular, methods for identification and growth of the actinomycetes are lacking.
I. The Actinomycetes
The actinomycetes (members of the order Actinomycetales) include a large variety of organisms that are grouped together on the basis of similarities in cell wall chemistry, microscopic morphology, and staining characteristics. Nonetheless, this is a very diverse group of organisms. For example, genera within this group range from the strict anaerobes to the strict aerobes. Some of these organisms are important medical pathogens, while many are saprophytic organisms which benefit the environment by degrading dead biological or organic matter. While many of these organisms grow optimally at temperatures common in the environment (e.g., 25-27xc2x0 C.), some organisms are quite capable of growing at the body temperature of most mammals (e.g., approximately 35-37xc2x0 C.). However, two genera of medically important actinomycetes (Thermomonospora and Micropolyspora) are true thermophiles, capable of growing at temperatures ranging to 50xc2x0 C.
Colonies may be bacterium-like (i.e., ranging from butyrous to waxy and glabrous), or fungus-like (i.e., heaped, leathery, membranous colonies that are covered with aerial hyphae). Many actinomycetes exhibit filamentous growth with mycelial colonies, and some actinomycetes cause chronic subcutaneous granulomatous abscesses much like those caused by fungi. Because of these similarities, the actinomycetes were long-regarded as fungi, rather than bacteria (see e.g., G. S. Kobayashi, xe2x80x9cActinomycetes: The fungus-like bacteria,xe2x80x9d in B. D. Davis et al., Microbiology, 4th ed., J. B. Lippincott Co., New York, 1990), pp. 665-671).
Despite their similarities with the fungi, the actinomycetes have typical prokaryotic characteristics in terms of nucleoid and cell wall structure, antimicrobial sensitivity, the absence of sterols, motility by means of simple flagella, and long filaments of the diameter of bacteria (approximately 1 xcexcm, compared to the larger fungal hyphae). Microscopically, the morphology of the aerobic actinomycetes varies widely between genera and species, although they are generally observed as gram-positive rods or branching filaments. Some genera never progress beyond a typical bacterium-like coccoid or bacillary form (e.g., Rhodococcus sp.), while others form filaments with extensive branching (e.g., Nocardia, Streptomyces, Actinomadura, and Nocardiopsis). Most are non-motile in their vegetative phase of growth. However, some genera tend to form branched filaments which eventually fragment into motile, flagellated cells (e.g., Oerskovia sp.) (see e.g., G. Land et al., xe2x80x9cAerobic pathogenic Actinomycetales,xe2x80x9d in A. Balows et al., Manual of Clinical Microbiology, 1991, pp. 340-359).
Most of the actinomycetes form spores, with the type of spore formation serving as a phylogenetic and taxonomic tool for separating the organisms into groups. The actinomycetes are highly diverse, with at least ten subgroups. They are also closely related to such organisms as the coryneforn group (e.g., Corynebacterium sp.), the propionic acid bacteria (e.g., Propionibacterium sp.), and various obligate anaerobes (e.g., Bifidobacterium, Acetobacterium, Butyrvibrio, and Thermoanaerobacter). The following table lists the organisms included in the suprageneric groups of actinomycetes as set forth in the most recent edition of Bergey""s Manual,vol. 4, (Stanley T. Williams, editor of vol. 4; John G. Holt, editor in chief, Bergey""s Manual(copyright) of Systematic Bacteriology, Williams and Wilkins, pp. 2334-2338 [1989]).
Although these organisms may often be identified to the genus level based on their morphology at the time of primary isolation, organisms that have been repeatedly transferred in the laboratory often do not retain their typical morphologic characteristics and must be identified biochemically, or by analysis of their membrane fatty acid composition. Serological methods for identification and differentiation are rarely used, due to the extensive degree of cross-reactivity among the actinomycetes (See e.g., G. S. Kobayashi, supra, at p. 666).
II. Importance of the Actinomycetes as Pathogens
Many of these organisms are soil-dwellers, with relatively little pathogenic capabilities. Indeed, the actinomycetes are among the most abundant of organisms in the soil, where they serve the important function of breaking down proteins, cellulose, and other organic matter. Nonetheless, some Actinomyces, Nocardia, and Streptomyces species are associated with diseases of medical and veterinary importance, especially in immunocompromised individuals. The spectrum of disease caused by the actinomycetes is extremely broad, with pathology that is dependent upon a combination of organism type, tissue involved, and the immune status of the host. In immunocompetent humans, the most common diseases are a non-invasive, acute or chronic allergic respiratory syndrome (e.g., farmer""s lung), and mycetoma. In immunocompromised individuals, infection often begins in the lung as an acute to chronic suppurative process, which may progress to cavitation and multi-lobular pulmonary disease. In these patients, infection may spread to other organ systems. Importantly, these organisms have a predilection for the central nervous system.
Several species of Actinomyces have been associated with actinomycosis in humans and other animals, with A. israelii being the most common human isolate, and A. bovis the most common cattle isolate. Actinomycosis is usually characterized by chronic, destructive abscesses of connective tissues. Abscesses expand into the neighboring tissues and eventually produce burrowing, tortuous sinus tracts to the surface of the skin, where purulent material is discharged. In cattle, the lesions are characteristically large abscesses of the lower jaw (hence the common name of the disease, xe2x80x9clumpy jawxe2x80x9d), usually with extensive bone destruction. As with most saprophytic organisms that occasionally cause disease, actinomycosis is not transmissible from person to person, nor between humans and other animals. Indeed, it is difficult to establish infection in laboratory animals.
For in vitro growth in the laboratory, these pathogenic organisms tend to be microaerophilic (e.g., require a decreased oxygen tension for optimum growth), require rich growth media, optimum incubation temperatures of 37xc2x0 C., and about 7 days of incubation. Although actinomycetes are soil organisms, actinomycosis is usually caused by endogenous organisms that have colonized the individual, rather than organisms from the environment. The organism is usually a conmuensal, which can be cultured from the tonsils of most humans, and is almost always present in teeth and gum scrapings. The conditions that lead to invasiveness are not well characterized, but may be multi-factorial, as actinomycotic infections are often mixed, with various organisms (e.g., Haemophilus actinomycetemcomitans, Eikenella corrodens, Fusobacterium, and Bacteroides) also present.
In contrast to the Actinomyces, diseases due to Nocardia sp. are associated with infection of the individual with soil organisms, rather than endogenous comnnensals. Nocardia are among the most clinically important actinomycetes, as they are responsible for the majority of disease associated with this group of organisms. Indeed, the term xe2x80x9cnocardiosisxe2x80x9d is often used synonymously for pulmonary and disseminated infection caused by any of the aerobic actinomycetes (see e.g., G. Land et al., xe2x80x9cAerobic Pathogenic Actinomycetales,xe2x80x9d in A. Balows et al., Manual of Clinical Microbiology, 5th ed., American Society for Microbiology, Washington, D.C., 1991, pages 340-359).
There are two common forms of disease associated with Nocardia sp., namely, pulmonary nocardiosis resulting from inhalation of the organism, and mycetoma, which is characterized by chronic subcutaneous abscesses resulting from contamination of skin wounds. These infections are usually serious, especially as they are frequently seen in association with immunosuppression or chronic underlying diseases (e.g., carcinoma, chronic granulomatous disease, Hodgkin""s disease, and leukemia). Once clinically evident, the progression of nocardiosis tends to be progressive and fatal, with approximately 50% of patients dying, even with aggressive therapy (see e.g., G.S. Kobayashi, xe2x80x9cActinomycetes: The Fungus-Like Bacteria, in B. D. Davis et al. (eds.), Microbiology, 4th ed., J. B. Lippincott Co., Philadelphia [1990], pages 665-671).
The Nocardia are aerobic organisms which grow on relatively simple media over a wide temperature range. As with the mycobacteria, growth in liquid media usually results in the production of a dry, waxy pellicle on the surface of the media.
The two species most commonly associated with human disease, N. brasiliensis and N. asteroides, share many other characteristics with the mycobacteria. For example, they are somewhat acid-fast, more easily stained with fuchsin, and their cell walls contain components characteristic of mycobacteria and corynebacteria (e.g., mycolic acid residues). Unlike the great majority of organisms, the somewhat harsh methods used to isolate mycobacteria (e.g., treatment of samples with N-acetyl-L-cysteine, and sodium hydroxide) are often successful for isolation of Nocardia. Extensive serologic cross-reactions in agglutination and complement fixation tests further indicate the relatedness of these groups of organisms.
The Streptomyces are also sometimes associated with actinomycotic abscesses. Mycetomas caused by streptomycetes are clinically indistinguishable from those caused by other actinomycetes. However, identification of these organisms can be critical, as they are generally not susceptible to antimicrobial agents. Therefore, treatment often entails surgical removal of the affected area or amputation.
Other members of the actinomycetes are capable of causing disease, including allergic respiratory disease (xe2x80x9cfarmer""s lungxe2x80x9d), which occurs in agricultural workers who inhale dust from moldy plant material. This syndrome has been associated with at least three thermophilic actinomycetes (Thermopolyspora polyspora, Micromonospora vulgaris, and Micropolyspora faeni). This disease is very similar to that caused by inhalation of allergens produced by various fungi, particularly Aspergillus sp.
In addition to the pathogenic potential of this group of organisms, there is also great interest in the particular genera which produce antimicrobial compounds.
III. Industrial Importance of the Actinomycetes
Ever since Waksman isolated actinomycin in 1940, and streptomycin in 1943, the streptomycetes have attracted a large amount of attention (see e.g., G. S. Kobayashi, et al., at p. 671). Thousands of soil samples collected world-wide have resulted in the identification of over 90% of the therapeutically useful antibiotics (see e.g., G. S. Kobayashi, xe2x80x9cActinomycetes: The Fungus-Like Bacteria, in B. D. Davis et al. (eds.), Microbiology, 4th ed., J. B. Lippincott Co., Philadelphia [1990], pages 665-671). The interest in improving antibiotic qualities and yields has resulted in various studies on this group of organisms, including improved methods for their growth and characterization.
It is important that strains be differentiated in screening programs to identify antibiotic activities, so that redundant testing is avoided. In addition, differentiation facilitates determination of taxonomic relationships which may lead to other organisms with promising activities. Unfortunately, testing of these organisms is often very difficult. Because they grow as filaments, they have a strong tendency to form clumps of mycelia which makes them much more difficult to handle, both in liquid cultures and on solid or semi-solid agar media. Furthermore, because of their complex life cycle which involves sporulation and germination, it is very difficult to obtain cultures which perform consistently in metabolic and biochemical testing programs. In addition, the presence of spores and the potential for their inhalation, represents a safety hazard to personnel responsible for the cultivation and characterization of these organisms, especially in settings where large-scale growth is necessary (e.g., antimicrobial production).
These growth characteristics also contribute to the difficulties associated with determining the susceptibility of the actinomycetes to antimicrobial compounds. The most frequently used testing methods are a modified Kirby-Bauer disk diffusion method agar dilution, and a minimal inhibitory concentration (MIC) method (see e.g., G. Land et al., xe2x80x9cAerobic Pathogenic Actinomycetales,xe2x80x9d in A. Balows et al., Manual of Clinical Microbiology. 5th ed., American Society for Microbiology, Washington, D.C., [1991], at p. 356). However, the success of these methods is contingent upon the production of a homogenized suspension for use as a standardized inoculum. Most commonly, agitation with sterile glass beads or a tissue homogenizer is used to prepare a homogenous suspension that can then be diluted to a 0.5 McFarland standard prior to inoculating the test media (see e.g., G. Land et al., xe2x80x9cAerobic Pathogenic Actinomycetales,xe2x80x9d in A. Balows et al., Manual of Clinical Microbiology, 5th ed., American Society for Microbiology, Washington, D.C., 1991, pages 340-359). These methods involving physical homogenization are very labor-intensive and tedious, and they result in damage, fragmentation, and death of some fraction of the cells. Furthermore, the additional manipulation required to produce a homogenous suspension prior to inoculation increases the risk of contamination of laboratory personnel and the laboratory environment.
Therefore, what is needed is a safe, reliable, easy-to-use system for the characterization and testing of medically and industrially important organisms, including but not limited to organisms such as the actinomycetes. In particular what is need is a rapid method that is readily automatable and useful in various settings (e.g., clinical, veterinary and environmental laboratories, and industry). Methods and compositions are also needed for high-volume, reliable analysis of strain differences between organisms.
The present invention relates to growing and testing any cell type in a multitest format which utilizes a gel forming matrix for the rapid screening of clinical and environmental cultures. In particular, the present invention is suited for the characterization of commonly encountered microorganisms (e.g., E. coli, S. aureus, etc.), as well as commercially and industrially important organisms from various and diverse environments. For example, the present invention is particularly suited for the growth and characterization of bacteria, as well as the actinomycetes and fungi (e.g., yeasts and molds).
In one embodiment, the present invention provides methods for testing microorganisms comprising the steps of: providing a testing means comprising redox purple and one or more test substrates; introducing microorganisms into the testing means; and detecting the response of the microorganism to the one or more test substrates. In a preferred embodiment, the testing substrates are selected from the group consisting of carbon sources and antimicrobials.
In an alternate embodiment, the testing means fiuther comprises one or more gel-initiating agents. In a preferred embodiment, the gel-initiating agent comprises cationic salts. In another alternative embodiment, the testing means further comprises one or more gelling agents. In a preferred embodiment, the microorganisms are in an aqueous suspension. In another preferred embodiment, the aqueous suspension fuirther comprises one or more gelling agents. It is contemplated that various gelling agents will be used with the present invention, including, but not limited to agar, gellan gum (e.g., Gelrite(trademark) and Phytagel(trademark)), carrageenan, and alginic acid.
In one embodiment of the method, the microorganisms are bacteria, while in another embodiment, the microorganisms are fungi. It is also contemplated that the methods of the present invention will be used with members of the Order Actinomycetales.
It is contemplated that various testing means will be used in the present invention. In one preferred embodiment, the testing means comprises at least one microplate (e.g., MicroPlate(trademark) microtiter plates, available from Biolog), while in an alternative embodiment, the testing means comprises at least one miniaturized testing plates or cards (e.g., MicroCard(trademark) test cards, available from Biolog). In yet another embodiment, the testing means comprises at least one petri plate.
The present invention also provides a kit, comprising redox purple and one or more test substrates. In a preferred embodiment, the test substrates are selected from the group consisting of carbon sources and antimicrobials. In another preferred embodiment, the kit further comprises one or more gel-initiating agents. In a particularly preferred embodiment, the gel initiating agent comprises cationic salts. In an alternative preferred embodiment, the kit further comprises one or more gelling agents. In another preferred embodiment, the gelling agent is selected from the group consisting of agar, gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid.
In another embodiment, the kit further comprises a suspension of microorganisms. In one preferred embodiment, the kit further comprises a testing means. It is contemplated that various testing means formats will be used successfully in various embodiments of the kits of the present invention, including microplates (e.g., MicroPlate(trademark) microtiter plates), miniaturized testing plates or cards (e.g., MicroCard(trademark) miniaturized test cards), petri plates, and any other suitable support in which the testing reaction can occur.
In yet another embodiment, the present invention provides a kit, comprising redox purple and one or more gelling agents. It is contemplated that various gelling agents will be used successfully in the various embodiments of the kits of the present invention, including but not limited to agar, gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In one preferred embodiment, the kit further comprises one or more gel-initiating agents. In a particularly preferred embodiment, the gel-initiating agent comprises cationic salts. In an alternative embodiment, the kit frther comprises a suspension of microorganisms.
In an alternative embodiment, the kit further comprises one or more test substrates. It is contemplated that the test substrates included in the kit of the present invention be selected from the group consisting of carbon sources and antimicrobials.
In yet another embodiment, the kit further comprises a testing means. It is contemplated that various testing means formats will be used successfully in various embodiments of the kits of the present invention, including microplates (e.g., MicroPlate(trademark) microtiter plates), miniaturized testing plates or cards (e.g., MicroCard(trademark) miniaturized test cards), petri plates, and any other suitable support in which the testing reaction can occur.
The present invention describes test media and methods for the growth, isolation, and presumptive identification of microbial organisms. The present invention contemplates compounds and formulations, as well as methods particularly suited for the detection and presumptive identification of various diverse organisms.
In order to characterize or identify organisms present in a sample, the present invention combines a gel-forming suspension with microorganisms that are already in the form of a pure culture. This is in contrast to the traditional pour plate method which involves heated agar and a sample that contains a mixed culture (see e.g., J. G. Black, Microbiology: Principles and Applications, 2d ed., Prentice Hall, Englewood Cliffs, N.J., p. 153 [1993]; and American Public Health Association, Standard Methods for the Examination of Water and Wastewater, 16th ed., APHA, Washington, D.C., pp. 864-866 [1985]).
It is also in contrast to the pour plate method of Roth (U.S. Patent Nos. 4,241,186, and 4,282,317), which utilizes a solidifying pectin substance. In the present invention, colloidal gel-forming substances are used at low concentrations, forming soft gels or viscous colloidal suspensions that do not need to, and in fact work best, when not completely solidified into a rigid gel.
In one embodiment, the present invention provides a method for introducing microorganisms into a testing device, comprising the steps of providing a testing device comprising a plurality of testing wells or compartments, wherein each compartment contains one or more gel-initiating agents; preparing a suspension comprising a pure culture of microorganisms and an aqueous solution containing a gelling agent, under conditions such that the suspension remains ungelled; and introducing the suspension into the testing device under conditions such that the suspension contacts the gel-initiating agents present in the compartments and results in the production of a gel or colloidal matrix.
In another embodiment, the present invention provides a method for testing microorganisms comprising the steps of providing a testing device comprising a plurality of testing compartments, wherein the compartments contain a testing substrate and one or more gel-initiating agents; preparing a suspension comprising a pure culture of microorganisms and an aqueous solution comprising a gelling agent under conditions such that the suspension remains ungelled; introducing the suspension into the compartments of the testing device under conditions such that the suspension forms a gel matrix within the compartment; and detecting the response of the microorganisms to the testing substrate. In one preferred embodiment, the testing device is a microplate (e.g., MicroPlate(trademark) microtiter plates).
It is contemplated that the microorganisms tested in this method will be bacteria, including members of the Order Actinomycetales, or fungi (e.g., yeasts and molds).
In one embodiment, the gelling agent is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In a particularly preferred embodiment, the gelling agent is carrageenan which contains predominantly iota-carrageenan. In one embodiment, the gel-initiating agent comprises cationic salts.
In one embodiment, the testing substrates are selected from the group consisting of carbon sources and antimicrobials. In yet another embodiment, the method further includes a calorimetric indicator, wherein the colorimetric indicator is selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators.
In yet another embodiment, the present invention encompasses a kit for growth and identification of microorganisms comprising: a testing device comprising a plurality of testing compartments containing one or more gel-initiating agents; and an aqueous solution comprising a gelling agent. In one preferred embodiment, the testing compartments ether contain testing substrates, such as carbon sources and antimicrobials. In one embodiment, the gel-initiating agent comprises cationic salts.
In one embodiment of this kit, the testing device is a microplate (e.g., MicroPlate(trademark) microtiter plates). In a preferred embodiment, the kit contains a gelling agent that is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In one preferred embodiment, the gelling agent is a carrageenan which predominantly contains the iota form of carrageenan. In one embodiment, the gel-initiating agent comprises cationic salts.
It is contemplated that the kit of the present invention will be used with microorganisms such as bacteria, including members of the Order Actinomycetales, as well as fungi (e.g., yeasts and molds).
It is also contemplated that the kit will also include a calorimetric indicator selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators.
In an alternative embodiment, the present invention comprises a kit for characterizing and identifying microorganisms comprising: a testing device containing a plurality of compartments, wherein the compartments contain one or more gel-initiating agents and one or more testing substrates, wherein the testing substrates are selected from the group consisting of antimicrobials and carbon sources and an aqueous suspension comprising a gelling agent.
In one embodiment of this kit, the testing device is a microplate (e.g., MicroPlate(trademark) microtiter plates), while in other embodiments, the testing device is a miniaturized testing plate or card (e.g., MicroCard(trademark) miniaturized testing cards). In a preferred embodiment, the kit contains a gelling agent that is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In one preferred embodiment, the gelling agent is a carrageenan which predominantly contains the iota form of carrageenan. In one embodiment, the gel-initiating agent comprises cationic salts.
It is contemplated that the kit of the present invention will be used with microorganisms such as bacteria, including members of the Order Actinomycetales, as well as fungi (e.g., yeasts and molds).
It is also contemplated that the kit will include a colorimetric indicator selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators.
The present invention also provides methods for comparing the function of a gene in at least two cell preparations, comprising the steps of: providing a testing device comprising a plurality of testing wells, wherein the wells contain a testing substrate and one or more gel-initiating agents; preparing a first suspension comprising a first cell preparation, in an aqueous solution comprising a gelling agent, and a second suspension comprising a second cell preparation in an aqueous solution comprising a gelling agent, under conditions such that the first and second suspensions remain ungelled; introducing the first and second suspension into the wells of the testing device under conditions such that the first and second suspensions form a gel matrix within the wells, such that the first and second cell preparations are within the gel matrix; detecting the response of the first and second cell preparations to the testing substrate; and comparing the response of the first and second cell preparations. In some embodiments, the first and second cell preparations comprise microorganisms selected from the group consisting of bacteria and fungi. In yet other embodiments, the first and second cell preparations contain cells of the same genus and species, while in still other embodiments, the first and second cell preparations contain cells that differ in one or more genes.
In alternative embodiments of the methods, the gelling agent is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In further embodiments, the testing substrates are selected from the group consisting of carbon sources, nitrogen sources, sulfur sources, phosphorus sources, amino peptidase substrates, carboxy peptidase substrates, oxidizing agents, reducing agents, mutagens, amino acid analogs, sugar analogs, nucleoside analogs, base analogs, dyes, detergents, toxic metals, inorganics, and antimicrobials. Indeed, it is not intended that the present invention be limited to any particular testing substrates, as it is contemplated that any testing substrate suitable for use with the present invention will be utilized. In still other embodiments, the gel-initiating agent comprises cationic salts. In some preferred embodiments, the methods further comprise a calorimetric indicator. In particularly preferred embodiments of the methods, the colorimetric indicator is selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators. In some particularly preferred embodiments, the oxidation-reduction indicator is tetrazolium violet, while in other embodiments, the oxidation-reduction indicator is redox purple. In yet other preferred embodiments, the testing device is at least one microplate (e.g., MicroPlatem microtiter plates), while in other preferred embodiments, the testing device is at least one miniaturized testing plate or card (e.g., MicroCard(trademark) testing cards). In further preferred embodiments, the response is a kinetic response.
The present invention also provides kits suitable for determining the phenotype of at least two organisms, comprising: a testing device containing a plurality of wells, wherein the wells contain one or more gel-initiating agents and one or more testing substrates; a first aqueous suspension comprising a gelling agent; and a second aqueous suspension comprising a gelling agent.
In one preferred embodiment of the kits, the testing substrates are selected from the group consisting of carbon sources, nitrogen sources, sulfur sources, phosphorus sources, amino peptidase substrates, carboxy peptidase substrates, oxidizing agents, reducing agents, mutagens, amino acid analogs, sugar analogs, nucleoside analogs, base analogs, dyes, detergents, toxic metals, inorganics, and antimicrobials. Indeed, it is not intended that the present invention be limited to any particular testing substrates, as it is contemplated that any testing substrate suitable for use with the present invention will be utilized. In alternative preferred embodiments of the kits, the gelling agent is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In still other embodiments of the kit, the gel initiating agent comprises cationic salts. In some particularly preferred embodiments, the testing device further comprises a colorimetric indicator selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators. In alternate preferred embodiments, the oxidation-reduction indicator is tetrazolium violet, while in other embodiments, the oxidation-reduction indicator is redox purple.
The present invention further provides methods and compositions for extrapolating the functions of genes or genetic sequences in various cell types. For example, the present invention provides methods for extrapolating the function of genes or genetic sequences in eukaryotic cells. In some embodiments, microbial genomes are examined to identify sequences that are homologous to the gene(s) or genetic sequence(s) of interest in the eukaryotic cell. Then, mutations are introduced into the homologous microbial gene. Next, the phenotypes of the wild-type and mutant microbial cells are analyzed and/or compared, as desired. In other embodiments, the functions of the microbial and eukaryotic genes are compared by utilizing genetic engineering methods to prepare transferable expression vectors (e.g., plasmids, phages, etc.) containing the eukaryotic gene(s) or genetic sequence(s) of interest. This expression vector is transferred into and expressed in a microbial host cell. The phenotype of the host microbial cell (ie., the cell containing the expression vector) and untransformed microbial cells (i.e., control cells comprising the same microbial cell line, but not containing the expression vector) are then analyzed and/or compared, as desired. In further embodiments, the vector comprises eukaryotic genes that have been modified (i.e., the genes are modified such that they are not the same as the wild type gene sequences).
The present invention also provides methods for comparing at least two cell preparations, comprising the steps of: providing a testing device comprising a plurality of testing wells, wherein the wells contain at least one test substrate selected from the group consisting of nitrogen sources, phosphorus sources, sulfur sources, and auxotrophic supplements; preparing a first suspension comprising a first cell preparation in an aqueous solution, and a second suspension comprising a second cell preparation in an aqueous solution; introducing the first and second suspensions into the wells of the testing device; detecting the response of the first and second cell preparations to the testing substrate; and comparing the response of the first and second cell preparations. In some embodiments of these methods, the first and second cell preparations comprise microorganisms selected from the group consisting of bacteria and fungi. In still other embodiments, the first and second cell preparations contain cells of the same genus and species, while in other embodiments, the first and second cell preparations contain cells that differ in one or more genes.
In certain preferred embodiments, the testing substrates further comprise substrates selected from the group consisting of carbon sources, amino peptidase substrates, carboxy peptidase substrates, oxidizing agents, reducing agents, mutagens, amino acid analogs, sugar analogs, nucleoside analogs, base analogs, dyes, detergents, toxic metals, inorganics, and antimicrobials. In further embodiments, the method further comprises a calorimetric indicator. In some preferred embodiments, the colorimetric indicator is selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators. In particularly preferred embodiments, the oxidation-reduction indicator is tetrazolium violet or redox purple. In yet other preferred embodiments, the testing device is at least one microplate (e.g., MicroPlate(trademark) microtiter plates), while in other preferred embodiments the testing device is a miniaturized test plate or card (e.g., MicroCard(trademark) miniaturized testing cards). In still other embodiments, the response is a kinetic response.
The present invention also provides methods for comparing the function of a gene in at least two cell preparations, comprising the steps of: providing a testing device comprising a plurality of testing wells, wherein the wells contain one or more gel-initiating agents, and at least one testing substrate selected from the group consisting of nitrogen sources, phosphorus sources, sulfur sources, and auxotrophic supplements; preparing a first suspension comprising a first cell preparation, in an aqueous solution comprising a gelling agent, and a second suspension comprising a second cell preparation in an aqueous solution comprising a gelling agent, under conditions such that the first and second suspensions remain ungelled; introducing the first and second suspensions into the wells of the testing device under conditions such that the first and second suspensions form a gel matrix within the wells, such that the first and second cell preparations are within the gel matrix; detecting the response of the first and second cell preparations to the testing substrate; and comparing the response of the first and second cell preparations. In some embodiments, the first and second cell preparations comprise microorganisms selected from the group consisting of bacteria and fungi, while in other embodiments, the first and second cell preparations contain cells of the same genus and species. In still other embodiments, the first and second cell preparations contain cells that differ in one or more genes.
In some embodiments of the methods, the testing substrates further comprise substrates selected from the group consisting of carbon sources, amino peptidase substrates, carboxy peptidase substrates, oxidizing agents, reducing agents, mutagens, amino acid analogs, sugar analogs, nucleoside analogs, base analogs, dyes, detergents, toxic metals, inorganics, and antimicrobials. In still other embodiments, the gelling agent is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In yet other embodiments, the gel-initiating agent comprises cationic salts. In some preferred embodiments, the method further comprises a calorimetric indicator. In some embodiments, the colorimetric indicator is selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators. In some particularly preferred embodiments, the oxidation-reduction indicator is tetrazolium violet, while in other preferred embodiments, the oxidation-reduction indicator is redox purple. In yet other preferred embodiments, the testing device is at least one microplate (e.g., MicroPlate(trademark) microtiter plates), while in other preferred embodiments the testing device is a mniniaturized test plate or card (e.g., MicroCard(trademark) miniaturized testing cards). In still other embodiments, the response is a kinetic response.
The present invention also provides kits for determining the phenotype of at least two organisms, comprising: a testing device containing a plurality of wells, wherein the wells contain one or more testing substrates selected from the group consisting of nitrogen sources, phosphorus sources, sulfur sources, and auxotrophic supplements; a first aqueous suspension; and a second aqueous suspension. In some embodiments, the wells of the testing device furter contain one or more gel-initiating agents, the first aqueous suspension further comprises a first gelling agent, and the second aqueous suspension further comprises a second gelling agent. In still other embodiments, the testing substrates further comprise substrates selected from the group consisting of carbon sources, amino peptidase substrates, carboxy peptidase substrates, oxidizing agents, reducing agents, mutagens, amino acid analogs, sugar analogs, nucleoside analogs, base analogs, dyes, detergents, toxic metals, inorganics, and antimicrobials. In yet other embodiments, the gelling agent is selected from the group consisting of gellan gum (e.g., Gelrite(trademark) and/or Phytagel(trademark)), carrageenan, and alginic acid. In further embodiments, the gel initiating agent comprises cationic salts. In still further embodiments, the testing device luger comprises a calorimetric indicator. In some preferred embodiments, the colorimetric indicator is selected from the group consisting of chromogenic substrates, oxidation-reduction indicators, and pH indicators. In some preferred embodiments, the oxidation-reduction indicator is tetrazolium violet, while in other preferred embodiments, the oxidation-reduction indicator is redox purple. In yet other preferred embodiments, the testing device is at least one microplate (e.g., MicroPlate(trademark) microtiter plates), while in other preferred embodiments the testing device is a miniaturized test plate or card (e.g., MicroCard(trademark) miniaturized testing cards). In still other embodiments, the response is a kinetic response.